/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the  "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id$
 */
package wx.xml.xalan.xml.utils;


/**
 * Simple stack for boolean values.
 *
 * @xsl.usage internal
 */
public final class BoolStack implements Cloneable {

    /**
     * Array of boolean values
     */
    private boolean m_values[];

    /**
     * Array size allocated
     */
    private int m_allocatedSize;

    /**
     * Index into the array of booleans
     */
    private int m_index;

    /**
     * Default constructor.  Note that the default
     * block size is very small, for small lists.
     */
    public BoolStack() {
        this(32);
    }

    /**
     * Construct a IntVector, using the given block size.
     *
     * @param size array size to allocate
     */
    public BoolStack(int size) {

        m_allocatedSize = size;
        m_values = new boolean[size];
        m_index = -1;
    }

    /**
     * Get the length of the list.
     *
     * @return Current length of the list
     */
    public final int size() {
        return m_index + 1;
    }

    /**
     * Clears the stack.
     */
    public final void clear() {
        m_index = -1;
    }

    /**
     * Pushes an item onto the top of this stack.
     *
     * @param val the boolean to be pushed onto this stack.
     * @return the <code>item</code> argument.
     */
    public final boolean push(boolean val) {

        if (m_index == m_allocatedSize - 1)
            grow();

        return (m_values[++m_index] = val);
    }

    /**
     * Removes the object at the top of this stack and returns that
     * object as the value of this function.
     *
     * @return The object at the top of this stack.
     * @throws EmptyStackException if this stack is empty.
     */
    public final boolean pop() {
        return m_values[m_index--];
    }

    /**
     * Removes the object at the top of this stack and returns the
     * next object at the top as the value of this function.
     *
     * @return Next object to the top or false if none there
     */
    public final boolean popAndTop() {

        m_index--;

        return (m_index >= 0) ? m_values[m_index] : false;
    }

    /**
     * Set the item at the top of this stack
     *
     * @param b Object to set at the top of this stack
     */
    public final void setTop(boolean b) {
        m_values[m_index] = b;
    }

    /**
     * Looks at the object at the top of this stack without removing it
     * from the stack.
     *
     * @return the object at the top of this stack.
     * @throws EmptyStackException if this stack is empty.
     */
    public final boolean peek() {
        return m_values[m_index];
    }

    /**
     * Looks at the object at the top of this stack without removing it
     * from the stack.  If the stack is empty, it returns false.
     *
     * @return the object at the top of this stack.
     */
    public final boolean peekOrFalse() {
        return (m_index > -1) ? m_values[m_index] : false;
    }

    /**
     * Looks at the object at the top of this stack without removing it
     * from the stack.  If the stack is empty, it returns true.
     *
     * @return the object at the top of this stack.
     */
    public final boolean peekOrTrue() {
        return (m_index > -1) ? m_values[m_index] : true;
    }

    /**
     * Tests if this stack is empty.
     *
     * @return <code>true</code> if this stack is empty;
     * <code>false</code> otherwise.
     */
    public boolean isEmpty() {
        return (m_index == -1);
    }

    /**
     * Grows the size of the stack
     */
    private void grow() {

        m_allocatedSize *= 2;

        boolean newVector[] = new boolean[m_allocatedSize];

        System.arraycopy(m_values, 0, newVector, 0, m_index + 1);

        m_values = newVector;
    }

    public Object clone()
        throws CloneNotSupportedException {
        return super.clone();
    }

}
